I'm quoting directly from the Workman Publishing Fall 2003 Catalog:

What is an owl pellet? It's the football-shaped object regurgitated twice a day by owls, which contains the skeleton of at least one owl meal, be it a mouse, vole, shrew, or small bird. Used in elementary schools to teach the "food web" - but virtually unavailable at retail - a professionally collected heat-sterilized owl pellet is now married to a lively two-color illustrated book filled with facts and related activities about these most amazing birds.

The book's called Owl Puke. We aren't carrying it.
My gramma was a science teacher for years, and I remember her collecting owl pellets with Flash. Still, that wasn't her packaging them and selling them to bookstores. I guess she missed a niche market.